The aim of this study has been to gain a fundamental understanding of the mechanisms and conditions
governing thermal degradation of poly (lactic acid) (PLA), poly (butylene-adipate-co-terephtalate) (PBAT)
and their blends upon processing conditions. Thermal degradation of biodegradable PLA and PBAT was
investigated firstly by thermal analysis and size-exclusion chromatography (SEC). It is shown that neat
polymers degrade upon processing hence the decrease of the molecular weight, rheological and
mechanical properties. Secondly, the reactive extrusion of polymers was performed with various
amounts of chain extension/branching agent, containing nine Glycidyl methacrylate (GMA) functions,
named Joncryl. The incorporation of this multi-functional oligomer showed an improvement of their
thermal stability. SEC and intrinsic viscosity measurements of these modified PLA and PBAT confirmed
the increase of viscosity and molecular weight probably related to the formation of extended and
branched chains. Rheological investigation of extended/branched PLA and PBAT as well as their modified
PLA/PBAT (80/20) (wt/wt) blends with various concentrations of GMA reactive functions exhibited higher
viscosity and storage modulus compared to the unmodified samples. This increase becomes more
pronounced as the concentration of Joncryl increases. Viscoelastic properties were assessed and related
to the molecular structure of modified polymers. Hence, the mechanisms of degradation, chain extending
with GMA functions and their competition have been proposed. The effect of reactive compatibilization
on the PLA/PBAT blends has been confirmed using transmission electron microscopy (TEM), scanning
electron microscopy (SEM) observations and tensile tests by the improvement of phase dispersion and
the increase of both Young’s modulus and strain at break.
The aim of this study has been to gain a fundamental understanding of the mechanisms and conditionsgoverning thermal degradation of poly (lactic acid) (PLA), poly (butylene-adipate-co-terephtalate) (PBAT)and their blends upon processing conditions. Thermal degradation of biodegradable PLA and PBAT wasinvestigated firstly by thermal analysis and size-exclusion chromatography (SEC). It is shown that neatpolymers degrade upon processing hence the decrease of the molecular weight, rheological andmechanical properties. Secondly, the reactive extrusion of polymers was performed with variousamounts of chain extension/branching agent, containing nine Glycidyl methacrylate (GMA) functions,named Joncryl. The incorporation of this multi-functional oligomer showed an improvement of theirthermal stability. SEC and intrinsic viscosity measurements of these modified PLA and PBAT confirmedthe increase of viscosity and molecular weight probably related to the formation of extended andbranched chains. Rheological investigation of extended/branched PLA and PBAT as well as their modifiedPLA/PBAT (80/20) (wt/wt) blends with various concentrations of GMA reactive functions exhibited higherviscosity and storage modulus compared to the unmodified samples. This increase becomes morepronounced as the concentration of Joncryl increases. Viscoelastic properties were assessed and relatedto the molecular structure of modified polymers. Hence, the mechanisms of degradation, chain extendingwith GMA functions and their competition have been proposed. The effect of reactive compatibilizationon the PLA/PBAT blends has been confirmed using transmission electron microscopy (TEM), scanningelectron microscopy (SEM) observations and tensile tests by the improvement of phase dispersion andthe increase of both Young’s modulus and strain at break.
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